The invention relates to a thermoplastic film for a laminated glass pane having a nonlinear continuous wedge insert in the vertical direction in some sections.
Laminated glass panes are currently used in many places, in particular in vehicle construction. Here, the term “vehicle” is defined broadly and relates, among other things, to road vehicles, aircraft, ships, agricultural machinery, or even work implements.
Laminated glass panes are also used in other fields. These include, for example, building glazings and also information displays, e.g., in museums or as advertising displays.
In these cases, a laminated glass pane generally has two glass surfaces that are laminated onto an intermediate layer. The glass surfaces themselves can have a curvature and are usually of constant thickness. The intermediate layer usually has a thermoplastic material, usually polyvinyl butyral (PVB), of a predetermined thickness, e.g., 0.76 mm.
Since the laminated glass pane is generally inclined relative to an observer, double images occur. These double images are caused by the fact that incident light usually does not pass completely through both glass surfaces, but instead that at least part of the light is first reflected and only thereafter passes through the second glass surface.
These double images are perceptible in particular in the dark, in particular with strong irradiating light sources, such as the headlights of an oncoming vehicle.
These double images are extremely bothersome.
Frequently, the laminated glass pane is also used as a head-up display (HUD) for displaying data. Here, an image is projected on the laminated glass pane using a projection device to display information to the observer in the field of view. In the vehicle sector, the projection device is, for example, arranged on the dashboard such that the projected image is reflected in the direction of the observer on the nearest glass surface of the laminated glass pane inclined relative to the observer.
Again, however, part of the light enters the laminated glass pane and is now, for example, reflected on the inner boundary layer of the glass surface located farther out from the perspective of the observer and the intermediate layer and then exits the laminated glass pane with an offset.
Here, also, a similar effect, the ghost image effect, occurs relative to the image to be displayed.
It must be noted that conventional compensation of the ghost image for one eye position always results in stronger ghost images for different eye positions. Also, a pure conventional compensation of ghost images results, under certain circumstances, in the fact that overcompensation for double images in transmission is observed.
This results in the fact that the respective observer is confused or, in the worst-case, receives incorrect information.
Previously, the attempt has been made to solve this problem by no longer arranging the surfaces of the glass surfaces parallel to each other but, instead, at a fixed angle. This is achieved, for example, in that the intermediate layer has a linearly increasing and/or decreasing thickness. In motor vehicle construction, the thickness is typically varied such that the smallest thickness is provided at the lower end of the pane toward the engine compartment, whereas the thickness increases linearly toward the roof. In other words, the intermediate layer has a wedge shape.
It has, however, been demonstrated that the prior art wedge-angle progressions can only inadequately minimize ghost images of head-up displays.
Based on this situation, one of the objects of the invention is to provide an improvement relative to double images and also ghost images.